The present invention relates to a varnishing film to be used for adjusting the surface gloss of prepress color proof. In more detail, it relates to a varnishing film to be used for forming an image with different glosses in particular areas on the surface of Surprint mode prepress color proof that is used mainly for proofreading operation during printing plate-making process, and a method of adjusting the surface gloss of prepress color proof using the same.
So far, there has been a method of forming a pattern on the surface of prints with resin, resin containing matting agent, etc. (overprint varnishing) to alter the surface gloss in that treated area, thus enhancing the printing effect, to raise the surface strength and to prevent the blocking (Printing Ink Technology, 413-417, written by E. A. Apps, Leonard Hill Limited, 1961).
On the other hand, so far, for color printing plate-making and proofreading of color printing, the prepress color proof by Surprint process using photosensitive transfer sheet that utilizes photosensitive resin etc. has been used (Japanese Unexamined Patent Publication Nos. Sho 60-28649, Sho 61-286857, Sho 62-103636, etc.).
Conventionally, however, there has been no method of performing a treatment equal to the overprint varnishing onto said prepress color proof by Surprint process. The invention addresses a subject to give an equal effect to overprint varnishing used on printing to prepress color proof by Surprint process, in particular, a subject to provide a method of altering the gloss in particular areas of image formed on the prepress color proof by Surprint process, thus enhancing the expression effect of prints.
As a result of diligent investigations to solve the subject aforementioned, the inventors have developed a varnishing film characterized by providing an adhesive transparent resin layer containing transparent matting agent and a transparent photosensitive layer on a transparent supporter. With such constitution, when the inventive varnishing film is imagingwise exposed to light and developed, the photosensitive layer in nonexposed areas is removed to expose the adhesive transparent resin layer containing transparent matting agent, resulting in decreased gloss in these areas. Consequently, the difference in glosses between exposed areas (area with remaining photosensitive layer) and nonexposed areas becomes significant, leading to an image excellent in the contrast.